1. Field of the Invention
This invention relates generally to the field of radiant energy responsive data card readers and specifically to data encoded cards in combination with readers.
2. Description of the Prior Art
Data card readers, capable of accepting and interpreting data encoded cards, are commonly used to input information to control systems. Applications for electronic control systems based upon data card input grow steadily as the convenience and cost of microprocessors and other computers becomes increasingly attractive. In control systems based upon data card input, often the most time consuming step of entering information involves proper orientation of the data card. An ideal data card reader would accept a data card in any orientation, would read the data rapidly and accurately, and would embody design simplicity consistent with an economical price tag.
Attempts to provide a card reader capable of extracting data from data cards positioned in other than a single orientation can be found in U.S. Pat. No. 3,673,389 to Kapsambelis et al., and in this applicant's previous application bearing Ser. No. 928,803 filed July 28, 1978, now U.S. Pat. No. 4,184,632.
The Kapsambelis patent provides the capability of reading a data card in any of four possible positions. However, a trinary coding system is used which requires extensive circuitry to interpret the card orientation data and further circuitry is needed in the computer or other electronic host to assimilate the data from the card in the proper order of significance. In addition, Kapsambelis utilizes a motor driven card reading mechanism, thus decreasing operating reliability.
This applicant's prior application provides a simplified device which reads a card in two of the four possible orientations but utilizes a physical stop to prevent insertion of the data card in the remaining two orientations. In addition, the accuracy of the card reader of the prior application is, to some degree, dependent upon the speed with which the data card is extracted from the reader, the alignment of the data card during reading, and improper overlapping of data perforations of opposed data tracks.